Sounds like there was some A/R factoring going on which IMHO should be illegal but it's not. That's when the doctors or hospital's "Sell" their A/R for pennies on the dollar to get rid of it, then the company that purchased them goes after the money, adding interest and finance charges to make a profit. Sounds crazy but it's not so unusual. The hospital or the physicians office that generated the charges still has the legal obligation to provide an itemized billing statement, I would start by finding out who the charges were from, calling them, getting an itemized billing statement and then contacting your insurance carrier to see if they have paid their portion. If they have not then I would go ahead and write them a letter along with the itemized bill and submit it to them for consideration. You have a better shot with the insurance carrier than the physician or supplier, as the insured. Anytime you get a hosp or medical bill where you decide to make a payment.. if the provider/hospital cash that check, that is considered a legally binding contract of payment. For example, if you have a $200 bill and you send in $20 towards that balance on the 15th of the month, and they cash that check, your payment obligation is $20 per month at that time of the month each month. Some hospitals and doctors WILL indeed send your check back with a counter offer, they won't cash the check and will send it back so that there is no legal obligation of taking that payment and so that they can legally submit to collection agencies where most times they have a better shot at collecting more. The collection agency that has these charges right now your disputing still have a legal obligation to provide you with the original creditor (supplier) so you can obtain the correct billing statement and take it from there.